Modular Notes

lifecycle.md

component/Lifecycle

• System construction and desctruction only
• Once your compnents have been created, they are on their own
  • i.e. it does not automatically add anything to a request/opartaion

Add something to every request

• Create a RingHandlerProvider designed to run just after the web server
• Intercept the handler
• Add wahtever you like to the request map and call the handler

(defrecord RingBinder []
  component/Lifecycle
  (start [this] this)
  (stop [this] this)

  RingHandlerProvider
  (handler [this] 
    (let [ring-handler-provider (find-ring-handler-provider this)
          ring-handler          (handler ring-handler-provider)
          ring-bindings         (get-ring-bindings this)]
      (fn [req] 
        (ring-handler (assoc req :params ring-bindings))))))

• Update the dependency map

(defn new-system []
 (let [system-map (component/system-map 
                   :webserver          (new-webserver :port 3000)
                   :ring-binder        (new-ring-binder)
                   :router             (new-bidi-ring-handler-provider)
                   :application-layout (new-layout :template "views/layouts/application.html.mustache")
                   :web                (new-web {:templates 
                                                      {:index (slurp "resources/views/index.mustache")}}))]
   (component/system-using system-map 
                           (-> {:webserver {:router :router}
                                :router    {:web :web}
                                :ring-binder {:web :web}} 
                               (interpose-component :webserver :application-layout)
                               (interpose-component :webserver :ring-binder)))))